1. Field of the Invention
The present invention relates to an ultrasonic imaging apparatus and an ultrasonic imaging method to be used for diagnosis of internal organs in living bodies or nondestructive inspection by transmitting and receiving ultrasonic waves.
2. Description of a Related Art
Various imaging techniques have been developed in medical field in order to observe and diagnose the inside of objects. Among the above-mentioned techniques, different from other medical imaging techniques such as X-ray photography and RI (radio isotope) scintillation camera, ultrasonic imaging, which transmits and receives ultrasonic waves and thereby obtains internal information of an object to be inspected, is free from exposure to the radiation ray. As a highly safe imaging technique, the ultrasonic imaging is used in a wide field including diagnosis of baby in the womb in obstetric field, gynecology, circulatory organs, digestive system and so on.
Further, in the ultrasonic imaging, different from the above-mentioned imaging techniques such as X-ray photography, it is possible to display ultrasonic information, which is obtained by using a probe, on a display apparatus in real time. Therefore, for example, the ultrasonic imaging is particularly advantageous in such cases when observing an organ of which state changes every second like circulatory system.
However, in the ultrasonic imaging, a patient as the object to be inspected is placed under restraint while observing the organs or the like, and therefore, a large physical load is imposed to the patient. In order to reduce the time required for ultrasonic imaging, it is conceivable that the intervals for scanning the object by using ultrasonic beam are made rougher uniformly. However, in this case, information from the depth of the object cannot be easily obtained. The reason of that is as described below. That is, the ultrasonic echoes reflected by a structure residing in a deep region of the object are faint, and also, they overlap with transmitting time zone of the ultrasonic beams to be subsequently transmitted or echoes of the subsequently transmitted ultrasonic beams from a shallow region, which makes it difficult to detect such the reflected ultrasonic echoes. Accordingly, it is desired to develop such an apparatus and method capable of performing ultrasonic imaging of an object entirely at a high speed while obtaining information necessary for diagnosis.